Tappets, such as fuel pump actuators, provide a mechanism to translate rotational motion of a rotating mechanism such as a cam into linear motion. In various configurations, tappets include a bearing, such as a needle bearing, fixed for rotation within an opening defined by a tappet body. Typically, such bearings are fixed for rotation by an axle or pin that extends on opposite ends through openings defined through the tappet body. These axles must be formed of a hard material that can withstand environmental conditions throughout the life of the tappet. In some configurations, the ends of the axles are upset to lock the axle relative to the tappet body at the openings. In some examples, high hardness upset methods currently available are not robust enough to avoid periodic loss of rotation freedom necessary to balance needle contact around the circumference of the pin.
The background description provided herein is for the purpose of generally presenting the context of the disclosure. Work of the presently named inventors, to the extent it is described in this background section, as well as aspects of the description that may not otherwise qualify as prior art at the time of filing, are neither expressly nor impliedly admitted as prior art against the present disclosure.